dashboard: derive ctx badge thresholds from the model context window

docs/web-ui.md

@@ -186,6 +186,13 @@ guess from container state.
   `ctx · Nk` chip showing the agent's last-turn context size
   (from `ContainerView.ctx_tokens`, read from the turn-stats
   sqlite on each `build_all` sweep; absent until the first turn).
+  The chip colour (green / yellow / red) is keyed off the model's
+  real context window: `build_all` resolves the last turn's model
+  against the host's per-model `contextWindowTokens` config and
+  exposes it as `ContainerView.context_window_tokens`; the badge
+  goes yellow ≥ 50% and red ≥ 75% of that window (the harness
+  compaction watermarks). When the window can't be resolved the
+  badge falls back to fixed 100k / 150k thresholds. (issue #66)
 - Line 2: action buttons — `↻ R3BU1LD` always, `DESTR0Y` + `PURG3`
   on sub-agents, `↺ R3ST4RT` + (sub-agents) `■ ST0P` when running,
   `▶ ST4RT` when stopped. Buttons dim + disable while a transient